The present disclosure relates to a method for placing a component on a substrate. A device suitable for placing a component on a substrate is provided with a component feeding device, a component pick-and-place device comprising a nozzle, a substrate carrier, means for moving the component pick-and-place device from the component feeding device to the substrate carrier and vice versa, as well as a global measuring system for determining the position of the component pick-and-place device during movement of the component pick-and-place device from the component feeding device to the substrate carrier and vice versa.
In such device, known from European Patent EP-B1-0.829.192, the component pick-and-place device is moved in X-direction over an X-slide, the ends of the X-slide being movable in Y-direction over two parallel extending Y-slides. The position of the component pick-and-place device in Y-direction is determined by the position of the X-slide with respect to the Y-slides. The position of the component pick-and-place device in X-direction is determined by the position of the component pick-and-place device with respect to the X-slide.
The accuracy with which a component carried by the nozzle of the component pick-and-place device can be placed on a substrate dependents on the accuracy with which the position of the component pick-and-place device with respect to the X- and Y-slides can be determined. Due to, amongst others, the relatively large number of parts between the Y-slides and the nozzle, the rigidity between the nozzle and the Y-slides is relatively low, so that the accuracy with which the nozzle can be moved with relatively high accelerations and the associated acceleration forces to a desired position is also relatively low. At the same time the known device is relatively sensitive to thermal effects, drift, creep as a function of time, for example, due to slip between the various parts etc. Moreover, due to the relatively great distance between the global measuring system and the nozzle, geometrical deviations can be transmitted enlarged, which is disadvantageous for the accuracy of positioning.
The object of the invention is to provide a device with which a component can be placed on a substrate in a relatively accurately way.
This object is achieved with the device according to the invention in that the device is further provided with a local measuring system, remote from the global measuring system, for substantially continually determining, in the proximity of a desired position of the component on the substrate, the position of the component pick-and-place device with respect to the substrate, which local measuring system is located closer to the substrate carrier than the global measuring system.
As the local measuring system is located closer to the substrate carrier, the number of parts present between the local measuring system and the nozzle is substantially lower, so that a higher rigidity and stability is achieved. Moreover geometrical deviations because of the shorter distance between the local measuring system and the substrate carrier have less or no impact. Therefore the accuracy with which the component can be moved to the desired position is higher.
An embodiment of the device according to the invention is characterized in that the local measuring system includes a grid located in the proximity of the substrate carrier, as well as at least one sensor that is connected to the component pick-and-place device, by means of which sensor the position of the component pick-and-place device can be determined with respect to the grid.
A grid includes a number of parallel extending reference lines, the distance of two adjacent reference lines defining the accuracy with which by means of the sensor the position of the component pick-and-place device can be determined. Such a grid can be positioned relatively easily near the substrate carrier. As soon as the component pick-and-place device, and accordingly the connected sensor is brought into the proximity of the substrate supported by the substrate carrier, the grid can be perceived by means of the sensor. As soon as the position of the component pick-and-place device is determined with respect to the grid, the component pick-and-place device can be moved accurately with respect to the grid. The grid can also include a different X-, Y-pattern that is recognizable to the sensor, like, for example, a kind of draught board.
Another embodiment of the device according to the invention is characterized in that the nozzle is at least moveable with respect to the component pick-and-place device in a plane extending parallel to the substrate carrier, wherein the sensor is connected to the nozzle.
In this manner it is possible to no longer move the component pick-and-place device in the proximity of the desired position on the substrate, but just to move the nozzle with respect to the component pick-and-place device, so that the mass to be moved is relatively small. Such small mass can be moved easily and accurately to the desired position by means of the sensor and the grid.
Yet another embodiment of the device according to the invention is characterized in that the component pick-and-place device is provided with a first imaging device for determining the desired position of the component on the substrate with respect to the grid.
Because both the first imagining device and the sensor are connected to the component pick-and-place device, is it possible to calculate the position of the substrate with respect to the grid by determining the position of the first imaging device with respect to the substrate and the position of the sensor with respect to the grid.
Yet another embodiment of the device according to the invention is characterized in that the device is provided with a second imaging device for determining the position of the component picked up by the nozzle of the component pick-and-place device with respect to the nozzle.
By means of the second imaging device the position of the component with respect to the nozzle can easily be determined. By also determining the position of the substrate with respect to the grid, it is subsequently possible to move the component accurately to the desired position on the substrate, using the sensor and the grid.
Yet another embodiment of the device according to the invention is characterized in that the device includes a reference element provided with one of at least a first and second marker, wherein during creation of an image of the component by means of the second imaging device at the same time images of the first and second marker are created by the first and second imaging device respectively.
By means of such reference element the position of the component can easily be determined with respect to the first imaging device, and subsequently with respect to the nozzle.
Another embodiment of the device according to the invention is characterized in that the reference element includes at least a third marker that is perceptible by means of the sensor during the creation of images by means of the first and second imaging devices.
Thus each time that the position of the component with respect to the nozzle is determined, the position of the first imaging device with respect to the sensor can be verified at the same time. If for instance, because of a rise in temperature and the subsequent expansions, the distance between the first imaging device and the sensor has changed, the distance between the sensor and the nozzle will have changed as well. By measuring this change, it can be taken into account while placing the component on the substrate.
The invention further relates to a method that is characterized in that during movement of the component pick-and-place device from the component feeding device to the substrate supported by the substrate carrier, the position of the component pick-and-place device is determined by means of the global measuring system, whereas in the proximity of the desired position of the component on the substrate, the position of the component pick-and-place device is almost continually determined by means of a local measuring system that is located closer to the substrate carrier than the global measuring system.
As the local measuring system is located closer to the substrate carrier, less parts need to be present between the local measuring system and the nozzle, as a result of which the nozzle and consequently also the component carried by the nozzle can be accurately moved to the desired position on the substrate.